1. Field of the Invention
The present invention relates to an image pickup apparatus which performs focus detection using light beams passing through pupil regions different from each other in an image pickup optical system.
2. Description of the Related Art
Previously, a focus detection method of using a phase difference detection method has been known. In the phase difference detection method, a light beam passing through an exit pupil of a lens is divided, and the divided light beams are received by a pair of focus detection sensors. Then, a drive amount of the lens required to achieve an in-focus state is obtained based on a shift amount of signals outputted depending on light receiving amounts of the divided light beams, i.e. a relative position shift amount of the light beams in a division direction. Accordingly, since an amount and direction of defocus is obtained when an accumulation is performed once by the focus detection sensors, a focusing can be performed at high speed.
Japanese Patent Laid-open No. 2000-156823 (paragraphs 0075-0079, and FIGS. 3 and 4, etc.) discloses a configuration in which a sensitive region of a light receiving portion is decentered with respect to an optical axis of an on-chip microlens in apart of light receiving elements (pixels) of an image pickup element to provide a pupil division function. These pixels are treated as focus detection pixels and are arranged, at predetermined intervals, between image pickup pixels in which a sensitive region of alight receiving portion is not decentered, to perform focus detection by the phase difference method. Since the region where the focus detection pixels are arranged is a defect section of the image pickup pixels, image information is interpolated by using information obtained from peripheral image pickup pixels.
Japanese Patent Laid-open No. 2001-305415 (paragraphs 0052-0056, and FIGS. 7 and 8, etc.) discloses a configuration in which a part of light receiving portions of pixels in an image pickup element is divided to provide a pupil division function. It also discloses a configuration in which outputs of the divided light receiving portions are independently processed to perform focus detection by a phase difference method and the outputs of the divided light receiving portions are added to be used as an image pickup signal.
Japanese Patent Laid-open No. 2010-140013 discloses a configuration in which images are added in an oblique direction considering an influence of vignetting to be able to perform focus detection for a periphery in a screen as well.
However, in each of the configurations disclosed in Japanese Patent Laid-open No. 2000-156823, Japanese Patent Laid-open No. 2001-305415, and Japanese Patent Laid-open No. 2010-140013, since the focus detection is performed by using one-dimensional image, it is weak in an object image with a repeated pattern, and an error remains, which is caused by influences of an adding direction of generating an image and an oblique line component included in the object. Therefore, particularly a focus detection accuracy in the periphery of the screen is deteriorated.